Breast Cancer Risk Elevated With Levonorgestrel-Releasing Intrauterine System Use

FRIDAY, Oct. 18, 2024 (HealthDay News) — Women using levonorgestrel-releasing intrauterine systems (LNG-IUS) have an increased risk for breast cancer, according to a study published online Oct. 16 in the Journal of the American Medical Association.

Lina Steinrud Mørch, Ph.D., from the Danish Cancer Institute in Copenhagen, Denmark, and colleagues examined breast cancer risk with continuous use of an LNG-IUS using data from nationwide Danish registers. All first-time initiators of any LNG-IUS aged 15 to 49 years in 2000 to 2019 were identified and matched to nonusers of hormonal contraceptives on the date of initiation (index date). The association between continuous LNG-IUS and breast cancer was examined, adjusting for confounding variables.

The analysis included 78,595 new LNG-IUS users and 78,595 nonusers of hormonal contraceptives. The researchers found that 1,617 participants were diagnosed with breast cancer during a mean follow-up of 6.8 years: 720 LNG-IUS users and 897 nonusers. The hazard ratio for breast cancer was 1.4 for LNG-IUS use versus nonuse. The hazard ratios were 1.3, 1.4, and 1.8 for zero to five, five to 10, and more than 10 to 15 years of use, respectively, compared with the corresponding durations of nonuse, resulting in an excess of 14, 29, and 71 breast cancer diagnoses per 10,000 users (P = 0.15 for trend).

“Given the increase in LNG-IUS use among females at an age with some risk for breast cancer, and its likely long-term use, information about breast cancer risk should accompany discussions about benefits and risks,” the authors write.

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